Glass is a material typically allowing light to pass therethrough, but the transmittance of glass is commonly about 90%, since about 8% of light is commonly reflected from the surface of glass, while the remainder of light passes through the glass.
In a glass plate, such as a glass cover of a photovoltaic cell or a display glass cover, requiring a high level of transmittance, an anti-reflective layer may be formed on the glass surface to improve transmittance.
Although specific types of processing, such as spraying, sol-gel processing, sputtering, and etching, may be used to form anti-reflective layers, anti-reflective in consideration of productivity, uniformity of anti-reflective layer, and degree of anti-reflective effect, anti-reflective layers may also be formed by etching.
Glass having an anti-reflective layer formed using a currently-available etching process has a relatively high level of transmittance of 97% or higher (about 94.5% when a single anti-reflective layer is provided on one surface), but may be easily fouled by impurities since relatively large pores are formed in the surface thereof.
To overcome the fouling problem, a fluoropolymer coating, the formation of concave and concave structures, and the like have been researched. However, there may be a problem with respect to long-term reliability, and the added process may lead to an increase in manufacturing costs.